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BAI TIU LUN KY THUT MI TRNGGVHD: PHAM XUN NUI

M U

T VN

Sn xut tinh bt khoai m l mt ngnh thc phm chnh ng Nam . Cng nghip

ch bin tinh bt khoai m l mt ngnh cng nng nghip lm theo thi v, s dng khoaim lm nguyn liu chnh. Tinh bt khoai m l mt trong cc ngun c hm lng tinh btcao nht, c khoai m cha n 30% hm lng tinh bt nhng c hm lng protein,cacbonhydrate v cht bo thp. l ngun thc n cho cuc sng con ngi v l ngunnguyn liu cho cc ngnh cng nghip ch bin thc phm.

Th trng tinh bt ngy cng tng do nhu cu s dng nguyn liu cho sn xut ngycng tng ca cc ngnh sn xut bnh ko, bt ngt...; c bit l nhu cu cho vic sdng sn xut nhin liu sch( nhin liu sinh hc).

Hin nay nc ta, trong cc ngnh cng nghip trng im ca t nc th tinh btsn l mt ngnh kinh t ang c s ch trng v thu ht u t ca cc nh sn xut.

c bit l lnh vc s dng nguyn liu sn cho cc nh my sn xut Etanol ang ngyc m rng v phm vi v quy m. N to ra nhng li ch kinh t, li ch x hi toln: to cng n vic lm cho ngi lao ng, ng gp cho ngn sch nh nc, n nhvn nguyn liu cho sn xut trong nc, qua n nh th trng. Tuy nhin cngvi s pht trin ca nh my, lun km theo nhiu vn bc thit cn gii quyt. Trong vn nc thi nh my c t ln hng u. Nguyn do y l ngnh sn xut sdng nc tng i ln, nc thi t qu trnh ch bin tinh bt sn gy nhim nguntip nhn cht hu c, dng thi phn hy sinh ra mi hi thi v mt s cht kh lm nhhng n mi trng khng kh. Nguy him hn khi nc thi c thi ra t qu trnhsn xut tinh bt sn, nu khng c x l trc khi ra mi trng s gy ra nhng tchi to ln cho con ngi, mi trng v sinh vt, do cha mt hm lng tng i

Xianua.p ng nhu cu thc t , chng ta s i tm hiu cng ngh x l Xianua t nc

thi trong qu trnh sn xut tinh bt sn nh my sn xut Etanol.

MC TIU V NI DUNG THC HIN

Mc Tiu Ca Ti

Nhom thc hin : 7 1Lp: Loc Hoa Du B-K53


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Xc nh thnh phn tnh cht nc thi sn xut tinh bt m.

X l cianua trong nc thi tinh bt sn

Ni Dung Thc Hin

Nghin cu c s l thuyt Thu thp cc phng n x l nc thi ngnh sn xut tinh bt

Thu th p cc phng n x l cianua trong nc thi

La chn cng ngh x l cianuaK HIU VIT TTBOD: Biochemical Oxygen Demand Nhu cuoxi sinh ho, mg/lCOD: Chemical Oxygen eman Nhu cu xi ho hc, m/lSS : Suspended Solid - Cht rn l lng, mg/lDO : Dissolved Oxygen Oxi ho tan, mgO2/lUASB: Upflow Anaerobic Susdge Blanket - X l ym kh ngc dng clp bn l lngFAO: T chc lng thc Th giiTCVN: Tiu chun Vit Nam

TBS: Tinh bt sn

CHNG I: TNG QUAN V NGNH SN XUT TINH BT SN

I.Gii thiu chung



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Tinh bt khoai m l thc phm cho hn 500 triu ngi trn Th Gii (theoCock,1985; Jackson & Jackson, 1990) c cc nc trn Th Gii sn xut v xutkhu. Brazil sn xut khong 25 triu tn /nm. Nigeria, Indonesia v Thi Lan cng snxut mt lng ln xut khu (CAIJ,1993). Chu Phi sn xut khong 85,2 triu tnnm 1997, Chu 48,6 triu tn v 32,4 triu tn do M La Tinh v Caribbean sn xut(FAO,1998). Nguyn liu ch bin Tinh bt khoai m t c m ti c cu to v thnh

phn nh sau:

1.Cu to c khoai m

Hnh 1.1 - Cu to c khoai m Cu to ca khoai m.

C khoai m c dng hnh tr, vut hai u. Kch thc c ty thuc vo thnh phndinh dng ca t v iu kin trng, di 0,1 1 m, ng knh 2 10 cm. Cu to gm4 phn chnh: lp v g, v ci, phn tht c v phn li.

2.Phn loi khoai m

C nhiu cch phn loi khoai m khc nhau, nhng ch yu l c phn ra t hailoi: khoai m ng v khoai m ngt. Vic phn loi ny ph thuc vo thnh phn

cyanohydrin c trong c m.Da vo thnh phn Cyanohydryn c trong c m m ngi ta phn n ra lm 2 loiKhoai m ng v khoai m ngt:

Khoai m ng (Manihot palmata Manihot aipr Pohl): Hm lng HCN hn50mg /kg c Khoai m ng c thnh phn tinh bt cao, s dng ph bin lm nguynliu cho cc ngnh cng nghip ch bin thc phm, cng nghip ho dc, cng nghipgiy v nhiu ngnh cng nghip khc.

Khoai m ngt (Manihot aipr hay Manihot utilissima Pohl): Hm lng HCN nhhn 50mg/ kg c. Khoai m ngt c dng lm thc phm ti v v ngt v d tothnh bt nho, d nghin nt hay nh nhuyn

Thnh phn ha hc c khoai m: thay i tu thuc vo ging, tnh cht, dinhdng ca t, iu kin pht trin ca cy v thi gian thu hoch

Bng 1.1 : Thnh phn ho hc cy khoai m



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3.Tnh hnh sn xut tinh bt sn Vit Nam v th gii:

Sn c s dng kh ph bin sn xut tinh bt, y l ngun nguyn liucho nhiu ngnh cng nghip nh cng nghip dt, thc phm, may mc, bnh ko, snxut ln men cn, sn xut acid hu c,...Bng 1. Din tch, nng sut v sn lng sn ca th gii t nm 1995 2008

Din tch(triu ha) Nm

Nng sut(tn/ha)

Sn lng(triu tn)

16,43 1995 9,84 161,7916,25 1996 9,75 158,5116,05 1997 10,06 161,60

16,56 1998 9,90 164,1016,56 1999 10,31 170,9216,86 2000 10,70 177,8917,17 2001 10,73 184,3617,31 2002 10,61 183,8217,59 2003 10,79 189,9918,51 2004 10,94 202,6418,69 2005 10,87 203,3420,50 2006 10,90 224,00

18,39 2007 12,16 223,7521,94 2008 12,87 238,45

Bng 2. Din tch, nng sut v sn lng sn ca Vit Nam giai on 1995 - 2008



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Nm Din tch(nghn ha)Nng sut

(tn/ha)Sn lng

( triu tn)

1995 164,30 9,84 1,621996 275,60 7,50 2,061997 254,40 9,45 2,401998 235,50 7,55 1,771999 226,80 7,96 1,802000 234,90 8,66 2,032001 250,00 8,30 2,072002 329,90 12,6 4,152003 371,70 14,06 5,23

2004 370,00 14,49 5,362005 425,50 15,78 6,722006 474,80 16,25 7,772007 496,80 16,07 7,982008 557,40 16,85 9,3

Bng 3.Din tch, nng sut v sn lng ca cc vng sinh thi Vit Nam nm 2008

TT Vng sinh thi Din tch(1000 ha)Nng sut(tn/ha)

Sn lng(1000 tn)

1 ng bng sng Hng 7,90 12,92 102,10

2 Trung du v min ni pha Bc 110,00 12,07 1.328,003 Bc Trung b v Duyn hi min

Trung168,80 16,64 2.808,30

4 Ty Nguyn 150,10 15,70 2.356,105 ng Nam B 113,50 23,74 2.694,506 ng bng sng Cu Long 7,40 14,43 106,80

C nc 557,40 16,87 9.395,80

Hnh 1.2. Gi tr kinh t ca c khoai m


C M TI


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c t CN: c t trong khoai m tn ti di dng CN-. Ty thuc vo ging v t

trng m hm lng c t trong khoai m khong 0,001 0,04%. Cyanua l nguyn tgy c tnh cao i vi con ngi v thy sinh vt. Cyanua t do tn ti di dng HCNhay CN- l dng c tnh nht trong nc l HCN. Cyanua ngn cn qu trnh chuynha cc ion vo da, ti mt, thn, nh hng n qu trnh phn ha t bo trong h thnkinh.. CN gy c tnh cho c, ng vt hoang d, vt nui.

4.Mt s quy trnh cng ngh sn xut tinh bt.


THC PHMBT CNG NGHIPRU CNNGISC VTThc phm trc tipBtSt ltVin nnBt bnNGNH CNG NGHIPGiyKeo ,HDt siG , vn pCao suGiyBT CNG NGHIP


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Mt s quy trnh cng ngh sn xut tinh bt khoai m trn th gii

Hnh 1.3: Quy trnh sn xut tinh bt ca Indonesia

Quy trnh ch bin c khoai m sn xut tinh bt c thc hin nh sau:


pLcBm nghinTinh btKhoai mSy khLngngQut htQut ht

nc


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Tch x, bLc, raTch ncPhi sySn phmdng tinh bt

Gel ha, pvin, sySn phmdng vin

ht(tapioca)

Mi xtBc v vra

Ra cC khoai m

Sng, lcNc cpKhithiH thng x lkhi

-X ra nguntip nhn

-S dng li ticy

LcNc thiTrm x l ncthi

Phi, my nnMi, nghinTrch ly, chic sutB mNc cpRa s b, tch tp chtBc v g, ra schBm nhSong chn rc,cng trnh x l s

b

Khoai m tiNc cpNc thiDehydrate haSy khng bao, v khoThnh phm



Nc cp


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Quy trnh cng ngh sn xut tinh bt ca Thi Lan



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Quy trnh cng ngh sn xut c p dng theo cng ngh ca Thi Lan, quy trnhng b khp kn, k thut tin tin mang tnh t ng ha cao, thc hin trch ly vhydrat ha sa bt nhiu ln lp i lp li, lm tng cht lng tinh bt v tng t l thuhi sn phm. Thi gian t khi nguyn liu nhp vo dy chuyn my mc n khi sn

phm ra khong 1 gi. Thao tc s dng v vn hnh my mc, thit b n gin, d thchin.

u im chnh ca cng ngh Thi Lan: Cng on trch ly chit sut c thc hinqua nhiu giai on, kt hp vi x l bt bng SO2. Do quy trnh cng ngh ca ThiLan cho t l thu hi h tinh bt cao, lng tinh bt to ra theo b c th hn ch ti mcthp nht.

II.Thnh phn v tc ng ca cc cht ha hc c trong nc thi nh my chbin tinh bt sn:1 .Thnh phn cc cht c trong nc thi ca nh my ch bin tinh bt sn

Nc sn xut c s dng nhiu nht cng on ra v ly tm tch b . Lngnc thi ra mi trng thng chim 80- 90 % nc s dng.

Nc thi sinh ra t dy chuyn sn xut tinh bt sn c cc thng s c trng nh:pH thp, hm lng cht hu c v v c cao, th hin qua hm lng cht rn l lng(SS), cc cht dinh dng cha N, P,K, cc ch s v nhu cu oxy sinh ho hc (BOD),nhu cu oxy ho hc (COD), mu...vi nng rt cao, vt nhiu ln so vi tiuchun mi trng. Nc thi c sinh ra t cc cng on sn xut chnh sau y:

- Bc v, mi c, p b: cha mt hm lng ln cyanua, alcaloid, antoxian, protein,xenluloza, pectin, ng v tinh bt. y l ngun chnh gy nhim nc thi, thngdao ng trong khong 20-25m3/ tn nguyn liu, c cha SS, BOD, COD rt cao.

- Lng trch ly: cha tinh bt, xenluloza, protein thc vt, lignin v cyanua, do cSS, BOD, COD rt cao, pH thp.

- Ra my mc, thit b, v sinh nh xng: c cha du my, SS, BOD.- Nc thi sinh hot (nc thi t nh bp, nh tm, nh v sinh) cha cc cht cnb, SS, BOD, COD, cc cht dinh dng (N, P) v vi sinh vt

- Nc ma chy trn ti nh my cun theo cc cht cn b, rc, bi.Ngoi ra, trong qu trnh sn xut, HCN ho tan trong nc ra b, thot khi dy

chuyn sn xut cng gp phn gy nhim mi trng to mu sm ca nc thi.Bn cnh nc thi cn c kh thi trong nh my sn xut tinh bt sn phi k n l

cc hp cht SOx t qu trnh ty ra dng nc SO2, dung dch NaHSO3, CO2 t qu trnhln men, cc loi kh NH4, indon, scaton, H2S, CH4 t cc qu trnh ln men ym kh vhiu kh cc hp cht hu c nh tinh bt, ng, protein trong nc thi, b thi. Cccht thi rn nh v snh (v lp ngoi cng ca c sn), cc phn s, b thi rn cha

nhiu xenluloza, b lc t my lc, my ly tm.Kt qu phn tch nc thi ti mt s doanh nghip sn xut tinh bt sn Vit Nam

(Bng 2).

Bng 2. Cht lng nc thi ca t sn xut tinh bt sn



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Ghi ch: * Cc thng s quy nh trong tiu chun, cha xt h s lin quan ndung tch ngun tip nhn v h s theo lu lng ngun thi, trong :

A - Thi vo ngun tip nhn dng cho mc ch sinh hot.B - Ngun tip nhn khc, ngoi loi A.C - Ngun tip nhn c quy nh.

Bng trn cho thy cht lng nc thi t quy trnh sn xut tinh bt sn hon tonkhng p ng c tiu chun mi trng. Ngoi tnh cht axit, nc thi cn chalng cht rn, cc cht hu c, HCN cn c x l. Bn cnh , khong cch dao

ng v cc ch tiu nc thi cao hn nhiu ln so vi tiu chun cho php. Thnh phnnc thi ph phuc vo quy m sn xut, tng mc u t, trnh cng ngh v hthng thit b x l nc thi, quy trnh vn hnh v quan trc mi trng. Vi hmlng BOD/ COD nh bng trn, nc thi ngnh sn xut tinh bt sn c th c x lym kh (UASB), hiu kh, h sinh hc, s dng ch phm vi sinh vt p ng cc tiuchun mi trng. Tuy nhin, nc thi sn xut tinh bt sn cc quy m khc nhau,hu nh cha t c tiu chun nc thi cng nghip ca Vit Nam.2 .Tc ng ca cc cht c trong nc thi

- Biochemical Oxygen Demand (BOD) l nhu cu oxy sinh ho hc xc nh mc nhim ca nc cp, nc thi cng nghip v nc thi sinh hot

- Chemical Oxygen Demand (COD) l nhu cu oxy ho hc oxy ho cc cht hu

c v v c cha trong nc thi cng nghipS nhim ca cc cht hu c dn n suy gim nng xy ha tan (DO) nc.

xy ha tan gim s tc ng nghim trng n h thy sinh, c bit l h vi sinh vt.Khi xy ra hin tng phn hy ym kh vi hm lng BOD qu cao s gy thi

ngun nc v git cht h thy sinh, gy nhim khng kh xung quanh v pht tn trnphm vi rng theo chiu gi.



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CHNG II : TNG QUAN CC PHNG PHP X L NC THITRONG NH MY SN XUT TINH BT SN

A.CC PHNG PHP X L:

I.PHNG PHP C HC :Phng php x l c hc s dng nhm mc ch tch cc cht khng ho tan v mt

phn cc cht dng keo ra khi nc thi .Nhng cng trnh x l c hc bao gm :

1.Song chn rc

2. B lng ct

3. B lng

4.B lng ng

5. B lng ngang

6. B lng ly tm

7. B vt du m

Hiu qu ca Phng php x l c hc :

C th loi b c n 60% tp cht khng ho tan c trong nc thi v gim BODn 30% . tng hiu sut cng tc ca cc cng trnh x l c hc c th dng bin

php lm thong s b, thong gi ng t sinh hc, hiu qu x l c th t ti 75%theo hm lng cht l lng v 40-50 % theo BOD.

Trong s cc cng trnh x l c hc c th k n b t hoi , b lng hai v , b lngtrong c ngn phn hu l nhng cng trnh va lng va phn hu cn lng .

II. PHNG PHP HA L

Bn cht ca qu trnh x l nc thi bng phng php ho l l p dng cc qutrnh vt l v ho hc a vo nc thi cht phn ng no gy tc ng vicc tp cht bn, bin i ho hc, to thnh cc cht khc di dng cn hoc cht hotan nhng khng c hi hoc gy nhim mi trng .Giai on x l ho l c th lgiai on x l c lp hoc x l cng vi cc phng php c hc, ho hc, sinh hc

trong cng ngh x l nc thi hon chnh .Nhng phng php ho l thng c p dng x l nc thi l : keo t, ng

t, tuyn ni, hp ph, trao i ion, thm lc ngc v siu lc

1. Phng php keo t v ng t

2. Tuyn ni



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3. Hp ph

4. Phng php trao i ion.

5. Cc qu trnh tch bng mng

6. Phng php in ho

7. Phng php trch ly

III.PHNG PHP HA HC

Cc phng php ho hc dng trong x l nc thi gm c : trung ho , oxy ho vkh . Tt c cc phng php ny u dng cc tc nhn ho hc nn l phng php ttin . Ngi ta s dng cc phng php ho hc kh cc cht ho tan v trong cc hthng cp nc khp kn . i khi cc phng php ny c dng x l s b trcx l sinh hc hay sau cng on ny nh l mt phng php x l nc thi ln cui

thi vo ngun .1. Phng php trung ho

2.Phng php oxy ho kh

3. Kh trng nc thi

IV.PHNG PHP SINH HC

Phng php x l sinh hc l s dng kh nng sng, hot ng ca vi sinh vt phn hu cc cht bn hu c c trong nc thi. Cc vi sinh vt s dng cc hp cht

hu c v mt s khong cht lm ngun dinh dng v to nng lng. Trong qu trnhdinh dng, chng nhn cc cht dinh dng xy dng t bo, sinh trng v sinh snv th sinh khi ca chng c tng ln . Qu trnh phn hy cc cht hu c nh vi sinhvt gi l qu trnh oxy ha sinh ha. Phng php x l sinh hc c th thc hin trongiu kin hiu kh( vi s c mt ca oxy) hoc trong iu kin k kh( khng c oxy).

Phng php x l sinh hc c th ng dng lm sch hon ton cc loi nc thicha cht hu c ho tan hoc phn tn nh. Do vy phng php ny thng c pdng sau khi loi b cc loi tp cht th ra khi nc thi c hm lng cht hu ccao.

Qu trnh x l sinh hc gm cc bc

Chuyn ho cc hp cht c ngun gc cacbon dng keo v dng ho tan thnhth kh v thnh cc v t bo vi sinh To ra cc bng cn sinh hc gm cc t bo vi sinh vt v cc cht keo v c

trong nc thi Loi cc bng cn ra khi nc thi bng qu trnh lng .

1. X l nc thi bng phng php sinh hc trong iu kin t nhin



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tch cc cht bn hu c dng keo v ho tan trong iu kin t nhin ngi ta xl nc thi trong ao, h ( h sinh vt) hay trn t ( cnh ng ti, cnh ng lc). H sinh vt

H sinh vt l cc ao h c ngun gc t nhin hoc nhn to, cn gi l h oxy ho,h n nh nc thi, x l nc thi bng phng php sinh hc. Trong h sinh vtdin ra qu trnh oxy ho sinh ho cc cht hu c nh cc loi vi khun, to v cc loithy sinh vt khc, tng t nh qu trnh lm sch ngun nc mt. Vi sinh vt s dngoxy sinh ra t ru to trong qu trnh quang hp cng nh oxy t khng kh oxy hocc cht hu c, rong to li tiu th CO2, photphat v nitrat amon sinh ra t s phn hu,oxy ho cc cht hu c bi vi sinh vt. h hot ng bnh thng cn phi gi gi tr

pH v nhit ti u. Nhit khng c thp hn 60C.Theo bn cht qu trnh sinh ho, ngi ta chia h sinh vt ra cc loi h hiu kh, h

sinh vt tu tin (Faculative) v h sinh vt ym kh. H sinh vt hiu kh

Qu trnh x l nc thi xy ra trong iu kin y oxy, oxy c cung cp qua

mt thong v nh quang hp ca to hoc h c lm thong cng bc nh cc hthng thit b cp kh. su ca h sinh vt hiu kh khng ln t 0,5-1,5m. H sinh vt tu tin

C su t 1.5 2.5m , trong h sinh vt ty tin, theo chiu su lp nc c thdin ra hai qu trnh : oxy ho hiu kh v ln men ym kh cc cht bn hu c. Trongh sinh vt tu tin vi khun v to c quan h tng h ng vai tr c bn i vi schuyn ho cc cht . H sinh vt ym kh

C su trn 3m ,vi s tham gia ca hng trm chng loi vi khun k kh bt bucv k kh khng bt buc. Cc vi sinh vt ny tin hnh hng chc phn ng ho sinh hc phn hu v bin i cc hp cht hu c phc tp thnh nhng cht n gin, d x

l . Hiu sut gim BOD trong h c th ln n 70%.Tuy nhin nc thi sau khi ra khih vn c BOD cao nn loi h ny ch ch yu p dng cho x l nc thi cng nghiprt m c v dng lm h bc 1 trong t hp nhiu bc .

Cnh ng ti - Cnh ng lcCnh ng ti l nhng khong t canh tc, c th tip nhn v x l nc thi. X

l trong iu kin ny din ra di tc dng ca vi sinh vt, nh sng mt tri, khng khv di nh hng ca cac hot ng sng thc vt, cht thi b hp th v gi li trongt, sau cc loi vi khun c sn trong t s phn hu chng thnh cc cht n gin cy trng hp th. Nc thi sau khi ngm vo t , mt phn c cy trng s dng.Phn cn li chy vo h thng tiu nc ra sng hoc b sung cho nc ngun .

2. X l nc thi bng phng php sinh hc trong iu kin nhn to B lc sinh hc

B lc sinh hc l cng trnh nhn to , trong nc thi c lc qua vt liu rn cbao bc mt lp mng vi sinh vt . B lc sinh hc gm cc phn chnh nh sau : phncha vt liu lc , h thng phn phi nc m bo ti u ln ton b b mt b , hthng thu v dn nc sau khi lc , h thng phn phi kh cho b lc .



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Qu trinh oxy ho cht thi trong b lc sinh hc din ra ging nh trn cnh ng lcnhng vi cng ln hn nhiu .Mng vi sinh vt s dng v xc vi sinh vt chttheo nc tri khi b c tch khi nc thi b lng t 2 . m bo qu trnhoxy ho sinh ho din ra n nh ,oxy c cp cho b lc bng cc bin php thng git nhin hoc thng gi nhn to .Vt liu lc ca b lc sinh hc c th l nha Plastic ,x vng gm , Granit B lc sinh hc nh git

B c dng hnh vung , hnh ch nht hoc hnh trn trn mt bng , b lc sinh hcnh git lm vic theo nguyn tc sau :

Nc thi sau b lng t 1 c a v thit b phn phi , theo chu k ti u nctrn ton b b mt b lc . Nc thi sau khi lc chy vo h thng thu nc v cdn ra khi b .Oxy cp cho b ch yu qua h thng l xung quanh thnh b .

Vt liu lc ca b sinh hc nh git thng l cc ht cui , ng knh trungbnh 20 30 mm. Ti trng nc thi ca b thp (0,5 1,5 m3/m3 vt liu lc /ng).Chiu cao lp vt liu lc l 1,5 2m. Hiu qu x l nc thi theo tiu chun BOD t

90% . Dng cho cc trm x l nc thi c cng sut di 1000 m3

/ng B lc sinh hc cao tiB lc sinh hc cao ti c cu to v qun l khc vi b lc sinh hc nh git , nc

thi ti ln mt b nh h thng phn phi phn lc .B c ti trng 10 20 m3 ncthi / 1m2b mt b /ng. Nu trng hp BOD ca nc thi qu ln ngi ta tin hnh

pha long chng bng nc thi lm sch . B c thit k cho cc trm x l di5000 m3/ng B hiu kh bn hot tnh B Aerotank

L b cha hn hp nc thi v bn hot tnh, kh c cp lin tc vo b trnu v gi cho bn trng thi l lng trong nc thi v cp oxy cho vi sinh vt oxyho cc cht hu c c trong nc thi. Khi trong b , cc cht l lng ng vai tr l

cc ht nhn cho cc vi khun c tr, sinh sn v pht trin dn ln thnh cc bng cngi l bn hot tnh. Vi khun v cc vi sinh vt sng dng cht nn (BOD) v cht dinhdng (N, P) lm thc n chuyn ho chng thnh cc cht tr khng ho tan v thnhcc t bo mi. S lng bn hot tnh sinh ra trong thi gian lu li trong b Aerotankca lng nc thi ban u i vo trong b khng lm gim nhanh cc cht hu cdo phi s dng li mt phn bn hot tnh lng xung y b lng t 2 , bngcch tun hon bn v b Aerotank m bo nng vi sinh vt trong b. Phn bnhot tnh d c a v b nn bn hoc cc cng trnh x l bn cn khc x l. BAerotank hot ng phi c h thng cung cp kh y v lin tc . Qu trnh x l sinh hc k kh - B UASBQu trnh x l sinh hc k kh

Qu trnh phn hy k kh l qu trnh phn hy sinh hc cc cht hu c c trongnc thi trong iu kin khng c oxy to ra sn phm cui cng l kh CH 4 v CO2(trng hp nc thi khng cha NO3- v SO42-).

B. QUY TRNH X L NC THI NH MY CH BIN TINH BT SN

I.S quy trnh x l nc thi:



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I. Thuyt minh quy trnh x l nc thiNc thi t qui trnh cng ngh c dn qua song chn rc loi b tp cht

th c kch thc ln sau nc thi c dn qua b gn bt thu hi lng tinh btc st li sau cng on ly tm, lng tinh bt ny thng nh hn nc, ni ln cvt em bn cho lm thc n gia sc, nc thi c dn qua b lng ct, ti y nhnght ct c kch thc ln hn 0,2 mm s c gi li trnh nh hng n h thng

bm cc cng trnh pha sau. Nc thi c dn qua b axt ha kh CN - vi thigian lu nc l hai ngy, sau khi ra b acid ha, nc thi c pha trn NaOH v chtdinh dng to mi trng thun li cho cng trnh x l sinh hc pha sau. Nc thitip tc a sang b UASB, pH thun li cho hot ng ca b UASB l 6,7 7,5. Ti bUASB, cc vi sinh vt dng k kh s phn hy cc cht hu c c trong nc thi, hiusut x l ca b UASB tnh theo COD, BOD t 60-80% thnh cc cht v c dngn gin v kh Biogas (CO2, H2S, CH4, NH3) theo phn ng sau:Cht hu c + vi sinh vt k kh CO2 + CH4 + H2S + sinh khi mi + Phn CN- cn li tip tc c phn hy b UASB.

Sau b UASB c thi dn qua b Aeroten x l trit cc hp cht hu c. Ti bAeroten din ra qu trnh sinh hc hiu kh c duy tr t my thi kh. Ti y cc visinh vt dng hiu kh (bn hot tnh) s phn hy cc cht hu c cn li trong ncthi thnh cc cht v c dng n gin nh: CO2, H2O Theo phn ng sau:

- S oxy ha tng hpCOHNS + O2 + dinh dng CO2 + NH3 + C5H7NO2 + cc sn phm khc

- Phn hy ni boC5H7NO2 + 5O2 5 CO2 + NH3 + H2O + nng lng

Qu trnh phn hy ca cc vi sinh vt ph thuc vo cc iu kin sau: pH, nhit ,cc cht dinh dng, nng bn v tnh cht ng nht ca nc thi. Do cn phitheo di cc thng s ny trong b Aeroten. Hiu qu x l COD trong b t t 90-95%.

T b Aeroten nc thi dn sang b lng, ti y din ra qu trnh phn tch gia ncv bn hot tnh. Bn hot tnh lng xung y. Nc thi c a n h sinh vttrc khi c x ra ngun tip nhn.

Bn hot tnh y b lng mt phn c bm tun hon v b Aeroten nhm duy trhm lng vi sinh vt trong b. Bn d c bm vo b nn bn trng lc lm gimth tch. Sau c bm n ngn khuy trn ca my lc p bng ti khuy trncng polyme, ri i qua h thng bng ti p bn. Bn thi ra c dng bnh em i chnlp hoc s dng lm phn bn.C th nhim v ca tng thit b:1. Song chn rcSong chn rc c nhim v gi li cc tp cht th c kch thc ln nh rc, v khoaim Cc tp cht ny c th gy ra s c trong qu tr nh vn hnh h thng nh lm tcng ng hoc knh dn, bo mn ng ng, thit b, tng tr lc dng chy nn lmtng tiu hao nng lng bm. Qu trnh ly rc

- Dng co ly rc khi cc thanh chn- Cho rc va co vo thit b cha rc



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- a n ni rc nhn vin v sinh mi trng n thu gom nh k hng ngyv ch n ni x l cht thi rn tp trung

- Chu k ly rc song chn rc ph thuc vo lng rc. Vic ly rc phi tin hnhng qui nh v rc ng qu lu khng nhng gy mi hi thi m cn gy cn tr dngchy t song chn rc n b lng2. B gn bt:

B gn bt c tc dng tch cc cn rn c kch thc ln v gn li vng bt niln trn, bt s c vt bng phng php th cng v em bn cho cc c s chnnui lm thc n gia sc.3. B lng ct

Loi b ct, cui v nhng mnh vn v c kh phn hy trong nc thi. Nu ctkhng c tch ra khi nc thi c th gy nh hng n cc cng trnh pha sau nhmi mn thit b, nhanh lm h bm, lng cn trong ng mng. Nn cn phi s dng blng ct m bo cho cc cng trnh x l tip theo t hiu qu tt hn v hot ngn nh hn.

B lng ct c tnh ton vi vn tc dng chy trong ln cc phn t hu cnh khng lng c v nh ct v tp cht rn v c gi li trong b.Trong b lng ct ngang, dng chy theo hng ngang v vn tc c kim sot theo

kch thc b, ca phn phi u vo v mng trn u ra. Vn tc chy thng gn bng0.15-0.3m/s, thi gian lu nc t 30 90s. Ct sau lng c ly ra khi b bng

phng php th cng, thit b bm thy lc hoc s dng cc thit b c kh nh gucp, bm trc vt, bm kh nn, bm phn lc. Ct sau c n sn phi ct.4. B Axit Ha

Do lu lng, thnh phn, tnh cht nc thi ca nh my sn xut tinh bt tythuc vo dy chuyn sn xut nn thng dao ng nhiu trong mt ngy m. nnh ch dng chy cng nh cht lng nc u vo cho cc cng trnh x l pha

sau, cn thit phi c mt b iu ha lu lng. Kh CN- c trong nc thi khoai m vx l mt phn nc thi. Ti b axt ha, COD gim t 10-30% v phn ln cc chthu c phc tp nh protein cht bo, ng chuyn ha thnh axt ng thi hu htCN- c kh ht trong b axt ha.Nc thi sn xut bt m c pH thp nn rt thch hp cho cc vi khun axt ha. Trong

b axt ha xy ra 3 qu trnh sau:- Qu trnh thy phn: Qu trnh thy phn cc cht hu c thng th kh chm. Tc

thy phn c qu nh bi pH, kch c ca cht nn, hiu qu ca cht nn.- Qu trnh axt ha: S to thnh axt ha c thc hin bi nhiu nhm vi sinh vt.

Phn ln l cc vi sinh vt ym kh, nhng mt s c th ty nghi thc l chng c thdng oxygen. S lng chng thng rt thp ch khong 1% trong tng s lng vi sinhvt. Sn phm ca qu trnh l cc axt bo d bay hi, ru, axt lactc, CO2

- Qu trnh acetate ha: Cc axt s b chuyn tip v dng acetate, nc v CO2 iu kin t nhin CN- c th phn hy cn thi gian kh di. in hnh l trong

5-7 ngy khong 30% CN- b phn hy. Ti b axt ha hm lng CN- c kh nhanhhn rt nhiu, thi gian 2 ngy l lng CN- s gim khong trn 50% v khong 30%COD b phn hy.Qu trnh kh COD



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Cht hu c phc tp cht hu c n gin CO2 + H2S + NH35. B UASB

T b axt nc thi c bm b k kh UASB. Nhim v ca qu tr nh x l ncthi qua b UASB l nh vo s hot ng phn hy cc vi sinh vt k kh bin i chthu c thnh cc dng kh sinh hc. Chnh cc cht hu c tn ti trong nc thi l chtdinh dng cho vi sinh vt.S pht trin ca vi sinh vt trong b chia thnh 3 giai on:

- Giai on 1: Nhm vi sinh vt t nhin c trong nc thi thy phn cht hu cphc tp thnh cc cht hu c n gin c trng lng nh nh: Monosacarit, aminoaxt to ra ngun thc n v nng lng cho vi sinh hot ng.

- Giai on 2: Nhm vi khun to men axt bin i hp cht hu c n gin thnhcc axt hu c l axt acetic, nhm vi khun ym kh to axt l nhm vi khun axt

focmo.- Giai on 3: Nhm vi khun to mtan chuyn ha hydro v axt acetic thnh kh

metan v cacbonic. Nhm vi khun ny gi l Mtan focmo. Vai tr quan trng ca nhm

vi khun Mtan focmo l tiu th hydro v axt acetic. Chng tng trng rt chm vqu trnh x l ym kh cht thi c thc hin kh mtan v cacbonic thot ra khi hnhp. Hiu qu x l COD l 60-80%.6. B Aeroten

Nc thi sau khi qua cc cng trnh x l c hc v sinh hc bc I nng ca cccht bn vn cn kh cao v vy nu p dng b aeroten c in thng thng x l skhng m bo tiu chun p dng v khng t hiu qu cao. Aeroten xo trn honton l mt gii php kh thng dng v phng php ny cho php nng BOD5 vo

b 1000 mg/l m hiu sut x l ca cng trnh vn m bo yu cu.7. B lng II:Chn b lng t II kiu b lng ly tm c tit din mt ct hnh vung.

Lng hn hp nc bn t b aerotank dn qua. Lng cht l lng c n trong ncsau khi qua b arotank v c c bn hot tnh n nng nht nh phn cui ca b bm tun hon li b aroten v phn d c a ra ngoi.B lng 2 s phn phi nc bng ng ng t tm b v thu nc ra bng mng thut vng quanh b.Trong b c thit b gt cn quay quanh trc t tm b gt cn lng y b v hthu cn. Bn h s c a n b nn bn.8. H Thc Vt

Nc thi sau khi qua b aerotank th hm lng nit, photpho cn rt ln chnh vvy ta s dng thm h thc vt vi cc loi thc vt nh lc b nh, bo tync thisau khi ra khi b hm lng nit v photpho s t tiu chun loi B.9. B nn bn

Tch bt nc do mt phn bn hot tnh t b lng 2, b UASB a vo, lm gim sb m ca bn, to iu kin thun li cho cc qu trnh x l bn phn tip theo.u im:

- Thi gian khi ng ngn, vic kim bn hot tnh khi ng d dng v sn c.- Hiu qu x l sinh hc cao.



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- C th tn dng c lng tinh bt tht thot, tn dng c lng kh CH4 lmnng lng.

- Nng xyanua trong nc thi ch bin tinh bt khoai m dao ng trong khong19 96 mg/L, vi gi c trng dao ng trong khong 22 34 mg/L. Tuy nhin, khmay mn l cc hp cht xyanua ny rt d t phn hy. Do , khi vn hnh h thngUASB trong dy gi tr nng xyanua trong nc thi th khng quan st thy bt knh hng bt li no n h thng, v nng xyanua u ra lun thp hn 1 mgCN-/L.Nhc im:

- Chi ph vn hnh ln.- Din tch xy dng ln.- Vn hnh i hi k thut cao- duy tr s n nh ca qu trnh x l k kh, phi duy tr c trng thi cn bng

ng ca qu trnh theo 4 phn nu (Thy phn, acid ha, acetate ha v methane ha).Mun vy trong b x l phi m bo cc yu t sau:+ Nhit

Nhit l yu t iu tit cng ca qu trnh, cn duy tr trong khong30350C.Nhit ti u cho qu trnh ny l 350C.+ pH

pH ti u cho qu trnh dao ng trong phm vi rt hp, t 6,5 n 7,5. S sai lchkhi khong ny u khng tt cho pha methane ha.+ Cht dinh dng

Cn cht dinh dng theo t l COD:N:P = (4001000):7:1 vi sinh vt pht trintt, nu thiu th b sung thm. Trong nc thi sinh hot thng c cha cc cht dinhdng ny nn khi kt hp x l nc thi sn xut v nc thi sinh hot th khng cn

b sung thm cc nguyn t dinh dng.

+ kim kim ti u cn duy tr trong b l 15003000 mg CaCO3/l to kh nng m

tt cho dung dch, ngn cn s gim pH di mc trung tnh.+ Mui (Na+, K+, Ca2+)

Pha methane ha v acid ha lipid u b c ch khi mn vt qu 0,2 M NaCl. Sthy phn protein trong c cng b c ch mc 20 g/l NaCl.IC50 = 4700 7600 mg/l.+ Lipid

y l cc hp cht rt kh b phn hy bi vi sinh vt. N to mng trn VSV lmgim s hp th cc cht vo bn trong. Ngoi ra cn ko bn ni ln b mt, gim hiuqu ca qu trnh chuyn i methane.i vi LCFA, IC50 = 5001250 mg/l.+ Kim loi nng

Mt s kim loi nng (Cu, Ni, Zn) rt c, c bit l khi chng tn ti dng h atan. IC50 = 1075 mg Cu2+ tan/l. Trong h thng x l k kh, kim loi nng thngc loi b nh kt ta cng vi carbonate v sulfide. Ngoi ra cn m bo khng chacc ha cht c, khng c hm lng qu mc cc hp cht hu c khc.



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- UASB c th gy ra qu trnh mtan ha khng hon ton; kt qu l pH gim, qutrnh sinh kh biogas gim v hiu qu x l COD cng gim. Gi tr pH u vo thp cth nh hng ng k n hot ng ca qun th vi sinh vt trong h thng UASB, doqu trnh mtan ha ch xy ra vi pH ti u trong khong 6,5-7,5. nh hng ny cngc th xy ra ngay khi pH khng qu thp khong 6-10. Kt qu nghin cu ch ra rngvi gi tr pH 6-10, cng gy nh hng bt li trong qu trnh vn hnh h thng, kt qul hiu qu x l COD v qu trnh sinh kh biogas gim mnh, ngay c khi vn hnh vi

pH nh trn ch ko di trong vng 4h.- Mc d h thng UASB cho hiu qu x l cht hu c rt cao, nhng hm lng

COD u ra thp hn 300 mg/L vn khng th t n trong trng hp p dng chonc thi ch bin tinh bt khoai m. t c tiu chun x thi Vit Nam, nc thisau x l bng h thng UASB cn phi phi c x l trit trc khi x vo nguntip nhn.

- Kt qu nghin cu ch ra rng cc ion [SO3] vi nng thp hn 64 mg/L khnglm gim c tnh ca xyanua (do hnh thnh thio-cyanate) m thay vo cn lm tng

thm c tnh ca n. Tuy nhin, s c mt Fe2+

s lm gim ng k c tnh ca xyanuac trong qu trnh thy phn ln trong qu trnh mtan ha do c s hnh thnh phc chtfero-cyanide. D vy, s gim c tnh ny cng khng th kch thch qu rnh phn hyxyanua nhanh hn.

C. CNG NGH THCH HP X L NC THI TINH BT KHOAI MNhng cng ngh truyn thng n gin khng p ng c nhu cu x l v qun l

nc thi phc v cho pht trin bn vng, in hnh l ngnh ch bin tinh bt khoai m



23/47


ti Vit Nam. Da vo cc kt qu nghin cu t c qui m phng th nghim, cngngh thch hp x l nc thi tinh bt khoai m c xut nh Hnh

Hnh: Cng ngh thch hp x l nc thi ch bin tinh bt khoai m.

y l cng ngh x l vi nhiu u im nh khng i hi qu nhiu nng lng,c th ti sinh nng lng t ngun kh biogas thu c, gim thiu ng k nhu cu sdng t rng ln cho h thng h sinh hc. Mt khc thc t cho thy rng hthng x l k kh cao ti thc s c hiu qu i vi nhng loi nc thi cha hmlng cht hu c cao. Tuy nhin, sau h thng x l k kh bao gi cng cn bc x ltrit tip theo. cng l l do ti sao cn phi p dng qu trnh x l trit vi hthng bn hot tnh hiu kh v sau l h thng h sinh hc t nhin, gim thiunng cht hu c v cht dinh dng n mc thp nht, t tiu chun x thi ncthi cng nghip hin hnh ti Vit Nam (ngun loi B). Giai on tin x l vi thit bUAF c cp n phn trn c th c xem l s la chn khng bt buc, bi vkt qu thc nghim cho thy rt r rng khng xy ra bt k tc hi nghim trng nodo cht rn l lng gy ra trong sut 300 ngy vn hnh h thng UASB vi hm lngcht rn l lng nh hn 1.800 mg/L.

Hin ti, mt h thng x l th im, cng sut 10 m3/ng c thit k v lp t(b qua thit b UAF). H thng x l ny c khi ng v vn hnh vo gia thng2 nm 2006 ti nh my tinh bt khoai m KMC, tnh Bnh Phc. Sau 73 ngy vn hnh,h thng UASB ang c vn hnh vi ti trng hu c trong khong 6,2 7,4kgCOD/m3.ng, hiu qu x l t c kh tt. Hm lng COD u vo gim t 3.020



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- axit xyanhydric (hay nitrifocmic) c cng thc ho hc HCN, trng lng phn t27. th khan l cht lng rt linh ng, t trng d=0,696. Nhit si 20 0C, ng c -140C, c mi hnh nhn, v rt ng, ho tan rt d trong nc v ru, l mt chtaxit yu c pK~9,4. Hi ca HCN c t trng d=0,968.

- Cc mui xyanua kim nh NaCN, KCN l cc mui tinh th trng, d b phn hutrong khng kh bi hi nc, Co2, SO2..., Tan rt tt trong nc, t tan trong ru, tantrong dung dch nc ru. Dung dch nc ca cc mui ny c tnh kim mnh.

- Mui xyanua ca cc kim loi kim th tan nhiu trong nc, xyanua ca cc kimloi khc tan t hn.

- Mui xyanua thu ngn Hg(CN)2 tan trong nc nhng l cht in ly yu.

- Xyanua trng thi t do CN rt c (gi chung l nhn ngn) nhng khi n lin ktbn trong phc, th d phc Fe[Fe(CN)6] th li khng c. V s phn ly ca phc qunh nn trong dung dch nng CN khng gy c.

- ixyan (CN)2 l cht kh c khng mu, mi hnh nhn, tan tt trong H2O v ru,(CN)2 hnh thnh do nhit phn mt s mui xyanua nh Hg(CN)2 hay oxy ho CuCNbng FeCl3. (CN)2 km bn, do b thu phn.

2. Tnh cht ho hc

- Axit xyanhydric v cc xyanua b oxy ho bi oxy trong khng kh chuyn thnhxianat:

2CN - + O2 2CNO-

- dung dch long 1:5000 trong 5 thng HCN b phn hu ht

HCN + 2H2O HCOONH4 (ammonium foocmic)

2HCN + 2H2S + O2 2HCNS + 2H2O (axit sunfoxyanhydric)

- Cc mui xyanua kim loi kim b dioxyt cacbon trong khng kh phn hu to thnhHCN.

2NaCN + CO2 + H2O 2HCN + Na2CO3

V vy phi bo qun mui kim loi xyanua trong thng kn, ch mt.

- Cc mui xyanua tan trong nc d to vi cc xyanua khng tan thnh cc ion phc.

- Axit nitric tc dng vi cc cht hu c nh axit malic, xitric, ancaloit, tanin cng tonn HCN. Qua ct ngha vic to nn cc glucosit xyanhydric mt s thc vt.

- Cc aldehyt, ng cng ph hu c HCN

C6H12O6 + HCN C7H13O6N

- Trong mt s cc cy ci, thc vt c cha cc dn xut hu c ca Axit xyanhydric,v d: hnh nhn ng, nhn qu mn, l trc anh o, r sn, mng tre na, nm, cc htl v cnh loi u phaseolus lunatus. Du hnh nhn ng c cha amogdalis



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C20H27NO11 do tc dng ca men emulsin hay synaptase s b thu phn v gii phngHCN:

C20H27NO11 + 2H2O C7H6O + 2C6H12O6 + HCN

Trong du hnh nhn ng c 1,5g du th c 0,24g HCN. Lng HCN cha trong

nm, su ht hnh nhn git cht mt em b. Trong ht u c cht phaseolumatinC10H17NO6 do tc dng ca men phaseosaponin s thu phn v gii phng HCN:

C10H17NO6 + H2O C6H12O6 + CH3 - CO - CH3 + HCN

3. c tnh ca axit xyanhydric v cc xyanua tan

3.1. c tnh

- Axit xyanhydric tc dng ln qu trnh h hp t bo bng cch lm t lit cc menst ca xyto erom oxydaza hoc men vacbua (Warburg). Do thiu oxy nn mu trongtnh mch c mu thm v c nhng triu trng ngt.

- Axit xyanhydric gy c nhanh qua ng h hp, vi liu lng 0,3mg/1kg trnglng c th c th gy cht ngay.

Nng t 0,12 - 0,15mg/l gy cht t 30 pht n 1 gi.

Qua ng tiu ho: liu lng gy t vong l 1mg/1 kg trng lng c th i vicc mui nh KCN, NaCN.

- Axit xyanhydric c th thm nhp vo c th ri gy ng c bng cch thm qua ccvt thng ngoi da.

Nng cho php tip xc nhiu ln trong khng kh l 10ml/m3 hoc 11mg/m3

khng kh 200.

3.2. Triu trng lm sng- Ng c cp: Xy ra khi ht phi hay ung phi liu cao HCN. Ng c xy ra rt

nhanh chng, cc trung tm hnh tu b t lit, ngi b nn bt tnh, co git v cc c bcng. S h hp b ngt qung v dng li, tim p rt nhanh v khng u, nn nhncht sau 1 - 2 pht.

- Ng c bn cp: Cc hin tng thng gp l chng mt, bun nn, au u, ccnim mc h hp b kch thch. Nn nhn s hi, lo lng nhng vn cn sng sut, sau xut hin ri lon thn kinh, co git, dn ng t, cng hm, hin tng ngt bt u, nnnhn cht sau 20 pht. Nu cp cu kp thi, nn nhn khng cht nhng tn thng tim,t lit b phn.

- Ng c thng din: Xy ra i vi nhng ngi lm vic thng xuyn ni ckh HCN bc ln. Cc hin tng r rt l au u, chng mt, nn v mt nhc.

3.3. Cch cp cu, iu tr

- Nu b ng c bng ng h hp: a bnh nhn ra khi vng nhim c, ngilm cp cu phi eo mt n phng. Tin hnh ngay h hp nhn to, cho th xy



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hoc cacbongen loi nhanh cht c qua ng phi. Tim cc thuc tr tim nhCaphein campho, niketamit. Nu tru tim, tim thng vo tim ubain.

ng thi vi vic lm cc cp cu, vn hi, h hp t bo cn tin hnh:

+ Tim tnh mch glutation liu 0,01

+ Tim cc cht to nn methemoglobin.

Cng c th iu tr bng cc cht to nn methemoglobin khc:

+ Tim tnh mch 5-10ml dung dch 2-3% natrinitrit sau tim tip vi ln na(liu khng qu 1-1,5g)

+ Tim tnh mch 50ml dung dch xanh metylen.

Ngoi ra c th dng cc thuc chuyn HCN thnh cht khng c nh tim natritiosunphat (20ml dung dch 25% vo tnh mch) c th ti 200ml.

- Nu ng c qua ng tiu ho th dng vi apomocphin gy nn. Ra d dy

vi dung dch 2% KMnO4, hoc vi pehyrol v cp cu nh nu trn.II .CC PHNG PHP PHT HIN V XC NH HM LNGXYANUA NHIM

1. Phng php nh tnh

pht hin xyanua ta dng cc phn ng sau

- To thnh mu xanh beclin

Fe2+ + 6CN - [Fe (CN)6]4-

4Fe3+ + 2 [Fe(CN)6]4- Fe4[Fe(CN)6]2 xanh beclin

Ly vo ng nghim 1ml dung dch nghin cu c cha CN - , tip thm vi gitNaOH, mt vi git mui st 2(FeSO4), un nng hn hp, sau axit ho hn hp bngHCl v thm mt vi git dung dch Fe3+(Fe2(SO4)3.H2SO4).

- Phn ng Chinha hay picrosodic:

Ly mt bng giy lc, ln lt nhng vo dung dch bo ho axit picric, xong nhngvo dung dch 10% Na2CO3, p kh bng giy lc v phi trong ti (giy c mu vng).Khi c HCN tc dng vo, giy chuyn sang mu vng cam r rt ca isopurprin.

tng nhn bit sau khi chun b giy th trn, tip tc nhng mt na bng giyvo axit axetic 10% trung ho cacbonat (vng ny tr nn c tnh axit s khng nhy

vi HCN). Khi c HCN tc dng bng giy c hai mu r rt.Phng php ny pht hin HCN trong khng kh, trong kho tng sau khi phun

thuc chng rp c cn HCN khng.

2. Phng php nh lng



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xc nh lng xyanua trong ngun nc, t ta dng phng php n gin v dthc hin nht l chun th tch. chun th tch xyanua dng phng phpchun iot hoc chun bc.

2.1. Phng php chun iot

Phn ng chun CN - + I2 + H2O CNO- + 2I - + 2H+

Khi ht CN - th I2 + tinh bt mu xanh

Trung ho dung dch cha CN -bng natri hydrocacbonat bo ho, tt nht l dngthng vi gam NaHCO3 bt, chun dung dch bng dung dch I2 0,1 N cho ti khi xuthin mu xanh ca ch th h tinh bt vi I2.

1ml dung dch I2 0,1 N tng ng vi 0,00135g HCN

2.2. Phng php chun bc nitrat

Phn ng chun 2CN - + Ag+ [Ag (CN)2] -

im cui chun xut hin kt ta do

[Ag (CN)2] - + Ag+ 2AgCN

Kim ho dung dch nh phn c cha CN - bng vi gam NaHCO3 bt, sau thmvi git NaCl lm tng ch th v chun bng bc nitrat cho ti khi xut hin kt takhng tan mu trng c.

1 ml dung dch AgNO3 0,1N tng ng vi 0,0054g HCN

III.CNG NGH X L XYANUA

1.La chn b Acid ho x l nc xianuaC s la chn b Acid ha x l CN-

Trong nc thi khoai m, CN- tn ti di dng linamarin, di tc dng ca enzimtrong mi trng acid, lianamarin b phn hy to thnh glucose, aceton v acidcyanhydric theo phn ng:



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Hnh : qu trnh phn hy CN t finamamin

Trong iu kin t nhin, lianamarin di tc dng ca enzim s chuyn ha theo cch:

CN- + 1/2 O2 + enzyme CNO-

CNO- + H2O NH3 + CO2

Hoc:

HCN + 2H2O NH4COOH

h thng t c hiu qu x l cao cn ch trng n giai on kh CN trc.

Trong iu kin t nhin , CN cng c th t phn hy nhng khng trit v i hikhong thi gian phn hy kh di (sau 5-7 ngy khong 30% CN b phn hy).

CN- l c i vi sinh vt, nu nng CN- trong nc thi cao s nh hng tiucc ti hiu qu x l ca cc cng trnh x l sinh hc do trc khi i vo cng trnh

x l, nc thi phi c kh CN-. c im nc thi tng hp nh my c gi tr pHthp vic kh CN- han tan c th kh thi trong b axit ha. Theo nghin cu ca phngth nghim Khoa Mi Trng, ti b acid ha hm lng CN- c kh nhanh hn tnhin rt nhiu, phn ln cc hp cht hu c kh phn hy trong nc thi tinh bt mtn ti di dng ng, tinh bt, protein, lipid, limarin b thy phn thnh cc hpcht n gin, HCN, cc acid bo, cc hp cht acetate Kh nng phn hy CN- ti baxit c biu din trong hnh sau.



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Hnh: th biu din kh nng phn hy CN- ti b acid ha

(Khoa mi trng H Bch Khoa Tp.HCM)

Hnh : th biu din kh nng phn hy CN ti b acid haTi b acid ha hm lng SS v COD c x l kh cao (10 30% COD c xl). h thng hot ng c hiu qu cn thit k b acid ha x l trit CN - vgim ti trng cho cc cng trnh x l sau.

2. Cc phng php x l xyanuaXyanua rt d b phn hu thnh nhng cht khng c bi cc tc nhn ho hc. V

vy, bin php x l ho hc cht c xyanua l n gin, r tin v d thc hin nht.Tuy nhin, tu tng trng hp c th ngi ta vn dng cc phng php x l khcnhau. Di y l mt s phng php x l:

2.1. Phng php oxy ho:

Xyanua d b oxy ho bi cc tc nhn oxy ho thng thng nh clo, hydropeoxyt,focmandehyt, permanganat, axit peoximonosunfuric (H2SO5), persunfat v.v...

Nguyn tc: oxi ha xyanua t do v phc ca n thnh hp cht t c hn, cyanathoc kh nit v cacbonic.Cht oxy ha c th l: nc Clo, H2O2, NaOCl, CaOCl2,KMnO4

iu kin tin hnh: oxi ho cc xyanua ph thuc vo:

Loi cht oxi ho s dng, nng xyanua t do v phc cht, pH ca dungdch.

Liu lng cht oxi ho quyt nh mc sch ca nc sau x l, nhngliu lng ny ph thuc vo nng xyanua v dng tn ti ca chng trong ncthi, vo pH v bin ng pH trong qu trnh x l. Nng xyanua cng longcng tn nhiu cht oxi ho. Nh vy mi oxi ho trit xyanua c.



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Hnh 5.1.Thit b lm sch nc thi theo chu k, c h thng cn bng v iuchnh. 1- my trn nc thi vi cht phn ng, 2-thng phn ng, 3-bn iu khin t

ng, 4-dng c o, 5-cn ong, 6-bm.

S cng ngh thit b lm sch nc thi xyanua c trnh by trn. C th vnhnh t ng, lin tc hay gin on, th cng. Trn nc thi vi cht phn ng hay

dung dch thi b bng khuy c, my trnkhng dng kh nn khuy.

2.1.1 Oxy ho bng kh clo, nc giaven hay clorua vi. Tc nhn oxy ho ychnh l hypocloril OCl - :



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Hnh 5.2.S cng ngh lm sch nc thi xyanua lin tc bng kh clo .

1-b gom nc thi, 2-b cha kim , 3- bn iu khin , 4-b cha oxit, 5- thit bphn ng, 6- trn, 7- bm.

c x l qua mt quy trnh hai giai on. Giai on u tin l oxy ha xyanuathnh xyanat bng cch s dng tc nhn oxy ha nh Clo hay Natri hydroclorit trongmi trng kim (pH cao). Giai on hai l oxy ha cyanat (t c hi hn cyanua) thnhcacbon dioxit v nit thng qua vic s dng nhiu hn Clo hay Natri hydroclorit pHthp hn so vi giai on u.

- Phn ng ha hc din ra trong giai on u nh sau:CN- + OCl- CNO- + C l-

NaCN + NaOCl NaOCN + NaCl

2NaCN + Ca(OCl)2 2NaOCN + CaCl2

2NaCN + Cl2 + 2NaOH 2NaOCN + 2NaCl + H2O

Vic oxy ho xyanua thnh xyanat din ra c l nh oxy nguyn t tch ra t cccht oxy ho, ch khng phi oxy phn t tch ra .

L u : Khi dng clo lng cng phi lu rng khi ho tan clo vo nc s xy ra hintng axit ho theo phn ng.

Cl2 + H2O HCl + HOCl .



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Tc l ngoi axit hipoclor cn to thnh axit clohidric. V vy khi dung clo lng oxy ho xyanua phi thng xuyn cho thm kim trung ho axit clohidric t do, nukhng s to ra cloxiyan mt sn phm c ca qu trnh oxy ha trc tip xyanua.

2CN- + Cl2 2ClCN

- Phn ng ha hc din ra trong giai on hai nh sau:

Natri xianat (NaOCN) t c hn nhiu v d phn hu to nn sn phm khng c.Thc hin quy trnh tiu hu pH = 11-12. pH = 5 - 8 xyanat c th b oxy ho tip:

2NaOCN + 3NaOCl + H2O 2NaHCO3 + N2 + 3NaCl

2NaOCN + 3Cl2 + 6NaOH 2NaHCO3 + N2 + 6NaCl + 2H2O

Nhng nu 8 < pH < 10 s xy ra phn ng ph bt li:

NaCN + NaOCl + H2O CNCl + 2NaOH (xyanua clorua d bay hi v rt c)v CNCl + 2NaOH + H2O NaOCN + NaCl + 2H2O

Bi vy qu trnh tiu hu phi khng ch pH = 11,5 khng xy ra phn ng phsinh ra CNCl. Sau khi phn hu ht (CN -, CNO-) c th h thp pH xung 5-8 phnhu trit CN- thnh nhng sn phm khng c.

Cc tc nhn oxy ho ny ph hu CN - rt mnh v trit nhng k thut thc hintng i ngt ngho. x l xyanua quy ra 1kg HCN cn dng 3,9 kg lng Clo. m bo thng phi dng gp i, khuy trong b ln lin tc trong mt gi. Trong qutrnh trung ho xyanua c to ra hydroxit Ca(OH)2, Pb(OH)2, Fe(OH)3, gi pH t 7,59 kim tra.

u im: Cng ngh c thit lp ttCyanate l tng i t c hi v tip tc b oxy ha thnh carbon dioxide v

nit pH thp hnNhc im : Tha hypocloric l c hi ; To sn phm c hi; chi ph t ; Clo phnng vi cc cht hu c hnh thnh cc hp cht Clo ; ngun hypocloric t.

2.1.2. Oxy ho bng ClO2

Clodioxyt c ch to ti ch bng tc dng ca mui NaClO2 vi Cl2 hay axit

clohydric:2NaClO2 + Cl2 2ClO2 + 2NaCl

5NaClO2 + 4HCl 4ClO2 + 5NaCl + 2H2O

Oxy ho CN - n cn t hn 1,2 kg ClO2/1kg CN -

Ni chung vic oxy ho CN - bng tc nhn ClO- phn t hoc dioxytclo phi thchin k nghim ngt khng gy c hi cho nhng ngi thao tc thc hin quy trnh.



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2.1.3. Oxy ho bng ozon

Ozon : - Ozon l cht oxy ho c hot tnh cao v ho tan trong nc ln.

Bn trong mi trng axit hn so vi mi trng kim.

Ozon l c kh nng oxy ho rt cao.

D dng nhng oxy nguyn t hot tnh cho cc tp cht hu c.

Tc nhn ny t c hi hn clo, thc hin n gin hn v oxy ho CN - trit thnhcht khng c.

Giai on 1: Ozon oxy ha trc tip xyanua to thnh cyanate:

CN - + O3 OCN - + O2

Giai on 2: Nu s dng hm lng ozon d th cyanate b oxy ha taonitrogen v carbonate (hoc bicarbornate, ty thuc pH) theo phng trnh phn ng:

OCN - + O3 + 2H2O NH3 + HCO3- + 1.5O2

Trong iu kin c bn, xyanat thy phn sn lng amoniac, sau b oxy ha biozon to thnh nitrate theo phng trnh phn ng sau y:

CNO- + OH- + H2O NH3 + CO32-

NH3 + 4O3+ O3 NO3-+ H2O+ 4O2+H+

Thi gian phn ng cho qu trnh oxy ha xyanua hon thnh nhanh chng trong mth thng l phn ng vi 10 n 30 pht thi gian lu l in hnh. Cc phn ng giaion th hai l chm hn nhiu vi giai on th nht. Phn ng ny thng c thchin pH 10-12 tc phn ng l tng i n nh. Nhit khng nh hng ntc phn ng ng k

Bng : x l xianua bng ozon

Kt qu cho thy rng qu trnh oxy ha ca cyanide ph thuc ca vic b sungozone. Qu trnh oxy ha ca cyanate bi ozone l mt phn ng chm so vi cccyanide, v do , cyanate tch ly trong khi xyanua gn nh l hon ton b oxy ha.



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Hnh: nh hng ca nng xianua ban u v t l ozon vo tc ca qu trnh oxyha xianua

Hnh: cho thy qu trnh oxy ha xyanua c tng cng bi tng t l ozone vkhng ph thuc vo nng xyanua ban u trong dung dch. l cng r rng t cons ny, l xyanua trong dung dch gim tuyn tnh vi thi gian, do cho thy rngtc qu trnh oxy ha l khng i v tng t l thun vi s gia tng t l ozone.

Thit b ozon ha c nhiu dng loi m, loi thp si bt...



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u im:

- T l dng: 4,6kg O3 cho 1kg CN Oxy ho nc thi xyanua bng Ozon , KMnO4,FeSO4, c nhiu u im v mt cng ngh hn dng clo v chng khng sinh ra cc hpcht trung gian bay hi. Oxy ho nc thi xyanua bng ozon thch hp cho trng hpcn x l khi lng nc thi ln m trong c cha cc cation ng, km nukhng c lm sch thm c th dng li nc sn xut ca xng.

- Gim c tng lng nc trong nc x l do phn hy c xyanua v ui cht oxi, nit v mt phn H2CO3.

- Ozon c sn xut t khng kh bng cch s dng mt my pht in ozon . Nng Ozone khc nhau, t 5 n 25 mg / l of air, depending on ozone generator parameters (airkhng kh, ty thuc vo cc thng s my pht in ozone ( khng kh, flow, generator

power, etc.) and concentratiodng chy, in my pht in, vv) v nng c threach35 mg/l with pure oxygen. t 35 mg / l vi oxy tinh khit.

- Ozone l mt tc nhn oxy ha mnh m, n cung cp advantage that little or nosecondary products are li th m t hoc khng c sn phm c hi c hnh thnh sau

khi x l nc thi c cha xianua- Khng i hi nhit cao v p lc.

Nhc im: sn sinh ra mt lng ammoniac, chi ph cht phn ng /thit b

2.1.4. Oxy ho bng hydroperoxyt (H2O2)



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Hydroperoxyt cng l cht oxy ho mnh lit CN - thnh cht khng c phn ngcn c xc tc. Cu 2+ (xc tc c x dng cho phn ng l kim loi chuyn tip nhng ha tan, vanadium, vonfram hoc bc nng 5 - 50 mg / L)

CN - + H2O2 OCN - + H2O

(pH=9-10 / cht xc tc)Sn phm ca phn ng H2O2 l cyanate (CNO-) l t c hi hn so vi xyanua 1.000

ln v thng c chp nhn cho x ra ngoi mi trng.

Ta phi duy tr pH = 9-10 trnh s hnh thnh ca kh hydrogen cyanide(HCN).

Tc phn ng c th c tng thm khi thay i mt s yu t nh:

+ Tng nhit

+ Tng liu lng cht xc tc

+ S dng H2O2 d tha.

V d: + Ti 25 C v khng c cht xc tc, chuyn i xyanua thnh cyanate t domt 2-3 gi.

+Ti 50 C, mt gi hoc t hn.+Khi thm 10 mg/l Cu s tng tc gp 2-3 ln, trong mt thi gian vt

qu 20% hydrogen peroxide s lm tng t l khong 30%.

Ngoi ra, cyanate c th b ph hy thng qua thy phn axit, to thnh carbondioxide v ammoniac. Phng trnh l:

OCN - + 2H2 O2 CO2 + NH3 + OH

PH cng thp, qu trnh thy phn cng nhanh hn: pH =2, thy phn CNO - trong 5 pht pH= 5 trong 60 pht pH =7 trong 22 gi

T l dng 3,3 lt H2O2 35%/1kg CN -

Vic dng H2O2 hay O3 c th oxy ho c phc xyano ca st rt bn v xyanua huc.

Vic la chn h thng peroxygen ph thuc vo :+ Thi gian phn ng.

+ Cc sn phm mong mun (cyanate, hoc CO2 v NH3).

+ Cc loi ca xianua ang c x l (t do, axit yu phn ly, hoc tr).



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+ Kh nng kinh t.H thng ny n gin, x l c xianua t do v hp cht ca xianua (vi km, ng,

hoc cadmium)Vi bt k h thng peroxygen, pH ca 10/09 nn c duy tr nu Xianua c mt,

trnh s hnh thnh ca kh hydrogen cyanide (HCN).

u im: d tha cht phn ng phn hy nc v oxy;Tng i n gin hotng;

Nhc im: cht phn ng tn km, yu cu o lng chnh xc.2.1.5.X l bng Acid Peroxymonosulfuric(Caro axit):

Caro axit l mt sn phm c hnh thnh t cn bng hydrogen peroxide v acidsulfuric, v thng c sn xut ti ch bng cch s dng mt my pht in, m-unnh gn :

H2O2 + H2SO4 H2SO5 + H2O

Qu trnh ny c s dng ti mt s a im hot ng tinh luyn vng ln nht thgii. Axit cho cc hot ng quy m nh hn, aixd Caro c th c chun b thng quathy phn ca ,v d: amoni persulfate :

(NH4)2S2O2 + H2O NH2HSO2 + NH2HSO2

(H2SO2 / hi)Vi acid Caro, vic chuyn i cyanide cyanate hon tt trong mt vi pht, theo

phng trnh sau:CN- + H2SO2 CNO- + H2SO4

(pH 10)

Vic b sung d tha axid Caro s thy phn cyanate thnh cacbonat v nit trongcng mt bc:

2OH- + 2CNO- + 3SO52- 2CO32- + N2 + 3SO42- + H2OTrong iu kin c tnh axit, mt lng nh axit Caro s l cn thit k t khi cyanate

thy phn (phn ng th hai di y) l tng tc rt nhiu. Cc phng trnh nh sau:2H+ + 2CNO- + 3H2SO5 2CO2 + N2 + 3H2SO4 + H2O

CNO- + 2H2O CO2 + NH2 + OH-

2.1.6. Oxy ho bng hydroperoxyt v natrihypoclorit H2O2 + NaOCl

2CN - + H2O2 + OCl - 2OCN - + Cl - + H2O

y khng i hi pH cao nh khi dng mt mnh mui hypoclorit, khng phithc hin ch pH nghim ngt phng sinh ra kh c. V khng cn thm nhiu

NaOH iu chnh pH nn tit kim c 30% chi ph.

2.1.7. Oxy ho bng H2O2 + HCHO (focmandehyt)

* Ring H2O2:



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CN - + H2O2 OCN - + H2O

* Ring HCHO:

CN - + H-C =O + H2O HO-CH2- C

N + OH-

H (glucolonitril)

[Zn(CN)4]2- + 4HCHO + 4H2O 4HO-CH2-C

N + 4OH- + Zn2+

* Hn hp H2O2 + HCHO:

HO-CH2-C

N + H2O HO - CH2 - C - NH2

xc tc OH- O

Di tc dng ca vi khun, sn phm ny phn hu thnh mui glucolat HO-CH 2 -COO- khng c hi.

2.1.8. Oxy ho bng KMnO4

Kh c nc thi bng KMnO4: thch hp cho nng sut nh v trang thit b vnhnh n gin nhng t do KMnO4 cao.

Oxy ho bng KMnO4 xc tc Cu2+

3CN - + 2MnO4- + H2O 2MnO2 + 3OCN - + 20H-

pH ca qu trnh l 9,5, pH cng cao th phn ng xy ra cng nhanh.

T l dng cn 4,05 kg KMnO4/1kg CN -. Nh vy dng tc nhn oxy ho ny kht v li nhng sn phm cha an ton cho mi trng.

Thit b dng thc hin qu trnh oxy ho thng l loi khuy trn nu cc chtphn ng l th lng hoc rn- lng v l loi thp nu l th lng- kh

2.1.9. Oxy ho bng oxy khng kh v than hot tnh khi c CuSO4 xc tc

than hot tnh

2CN - + O2 2OCN -

Cu2+

OCN - +H2O HCO3- + NH3

HCO3- + OH - CO3 2- + H2O

2Cu2+ + 2OH- + CO3 2- CuCO3. Cu(OH)2

Vic xut hin kt ta cacbonnat baz cho thy xianat b thu phn; c th thm Cu2+

b sung cht xc tc.



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2.1.10. Xuc tc quang Titanium dioxide

Trong vi nm qua, xc tc quang bng cht bn dn a tinh thsemiconductorsirradiated by near-UV light has been c chiu bi nh sng a tinh thsemiconductorsirradiated by near-UV light has been gn c found effective in oxidizing certain

organic pollutantstm thy, c hiu qu trong vic oxy ha cc cht nhim hu c nhtnh n ccless dangerous species under mild reaction conditions. loi t nguy him hntheo cc iu kin phn ng nh . This method is found to be suitable for the oxidationoPhng php ny c tm thy l thch hp cho qu trnh oxy ha ca both free andcomplexed cyanides dissolved in wa xianua t do v c xianua complexed ha tan trongnc cht thiwater (Mills and Le Hunte, 1997).. The process works byQu trnh nyhot ng bng cchsubjecting wastewater to the combined forces of sun-chc cho ncthi kt hp vi light and a semiconductor catalysnh sng mt tri v mt cht xc tc

bn dn. Cht xc tc A commonly usexuc thng c s dng catalyst is titaniumdioxide (TiOl titanium dioxide (TiO22)). This catalyst may beCht xc tc ny c thc mixed into the water, creating a slurry, or fixed onto atrn ln vo trong nc, vic

to ra mt bn, hoc c nh vo mt lattice-type structure through which the water flowsor kiu cu trc mng tinh th nc chy thng qua hoccan be used in colloidal form.c th c s dng dng keo. When exposed to theKhi tip xc vi sunlight, thecatalyst absorbs the high-energy photonsnh sng mt tri, cht xc tc hp th cc

photon nng lng cao from the UV portion of the solar spectrum, and reactivt phn tiacc tm ca quang ph mt tri, to ra cc gc hydroxyl. Theseradicals are powerfuloxidizers that break down thCc gc t do l oxidizers phn hy cyanide where the first

product of photocatalytic oxida-mnh m cyanide v sn phm u tin ca qu trnh oxyha xc tc quang hc ca xianua trong s hin din ca TiO2 a tinh th 2in aqueousmedium is CNO trong mi trng nc l CNO-

u im: loi b hon ton sn phm khng mong munNhc im: kh vn hnh; chi ph tn km; yu cu nng lng cao(Augugliaro et al.,1999).2.2. Phng php in phn

Phng php ny d dng lm sch nc thi ca nhiu xyanua t cc b ra ngcchiu, nhiu bc hoc cc dung dch xyanua hng cn hu b, c nng xyanua khngdi 500- 600 mg/l. Khi x l s sinh NH4+, xyanat, Na2CO3, ure, trn catot thng ckim loi thot ra. Anot c th l thp khng g. Nc thi cha nhiu xyanua nn chothm NaCl hoc NaOH ri mi in phn v khi ti anot ngoi oxy cn c ion ClO -,lm tng thm tc dng oxi ho nng cao hiu qu lm sch nc v tit kim in nng

tiu th. oxy ho 1g xyanua cn t 0,4 n 2kWh. Khong cch gia ant v catot l30-50mm. Mt dng in 1-2 A/dm2. Mui NaCl 3-6 g/l.

2.2.1. in phn dung dch cha CN-

Trong mi trng kim (baz) dng cc CN - c oxy ho thnh xianat:

CN - + OH- OCN - + H2O+2e

[Zn(CN)4]2- + 8OH - Zn2+ + 4OCN- + 4H2O + 8e



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Xianat c to thnh b phn hu oxy ho:

2OCN - + 6OH- 2HCO3- + N2 + 3H2O + 8e

Nu dung dch c nng CN - qu thp nn dng H2SO5 hay H2S2O8 oxy ho.

2.2.2. in phn dung dch cha CN

-

c thm NaCl (3-5%)Thc cht y l trng hp oxy ho CN -bng NaOCl v trong dung dch khi in phn th NaCl NaOCl, v:

CN + OCl- OCN - + Cl -

H2O + 2OCN - + 3ClO- 2CO2 + N2 + 3Cl - + 2OH-

Cch ny u tin hn cch in phn trc tip v n c th x l c nc thi chanhiu hoc t xyanua u tt. Thit b ch to NaClO kh n gin, c th tn dng thit

b c sn v lp t ngay ti trm x l nc. Thit b cn c dung tch ln chac 1-5kg clo hot tnh. C 1kg clo hot tnh cn n 8- 10kwh in nng v 5-7kg

mui n.Sau khi oxi ha xyanua cn phi tch kim loi nng trong nc thi. Khu ny c

tin hnh ng thi vi vic lm sch nc thi kim-axit ca xng hay nh my.

2.3. Phng php to phc kt ta

y l phng php c in nhng c u im l chi ph thp v d thc hin. Tcnhn to phc kt ta l mui sunphat st hai hoc hn hp st hai v st ba. Cc phnng din t nh sau:

Trong mi trng kim (baz) FeSO4 tc dng vi CN -

Fe2+

+ 2CN-

Fe (CN)2Fe (CN)2 + 4CN - [Fe(CN)6]4-

[Fe(CN)6]4- + 2Fe2+ Fe2 [Fe(CN)6]

Phn ng tng cng:

3Fe2+ + 6CN - Fe2 [Fe(CN)6]

T l dng: 5,35 kg FeSO4 cho 1 kg CN -

Thc t trong dung tch c ln Fe3+ nn kt ta c mu xanh prusse hoc khi dngthm mui Fe (SO4)3.H2SO4 ta thu c kt ta xanh prusse.

[Fe(CN)6]4 - + Fe3+ Fe[Fe(CN)6]-M+Cc kt ta c tch khi nc bng phng php lng hoc lc

2.4.Sc khng kh vo nc thi nhim

Gii php n gin nht kh c xyanua l sc khng kh vo nc nhimxyanua. Nh m nc hp ph CO 2 to ra H2CO3 axit cacbonic l loi axid yunhng n vn mnh hn axit HCN v nh vy n s y HCN t mui xyanua. HCN



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hoc l bay hi hay chuyn ha thnh HOCN t c hi hn. Sau HOCN vi s c mtca oxy phn t s chuyn ha hay thy phn thnh amonic v CO2:

HOCN + H2O CO2+ NH3T hai phn t NH3 v mt phn t CO2 s to ra (NH4)2CO3 mt phn t CO2 d s

ha tan trong nc v li chuyn ion xyanua thnh HCN. Nh vy qu trnh kh xyanuatrong nc thi s din ra rt thun li do t cp c ngun CO 2 qu trnh phn ngdin ra nhanh v c hiu qu ngi ta phi sc khng kh nn vo nc nhim.

V hm lng CO2 trong khng kh thp nn lc u phn ng to ra HCN din ra rtchm chp, tuy nhin v sau CO2 c to ra ngay trong qu trnh kh xyanua nn

phn ng ni trn s c duy tr. Sc kh nn vo nc nhim l vic tng i d lmnh my nn tuabin, cc thit b chy bng thy lc hay sc gi.

2.5.phng php sinh hc :Enzyme x l cht thi xyanua, Cyanide hydratase (cngngh mi)

Cyanide hydratase, hoc formamide hydro-lyase l mt enzyme c kh nng chuyn

ho cyanide trong nc thi cng nghip thnh amoniac v formate thng qua mt bcphn ng. Cyanide hydratase c phn lp t mt vi loi nm v c to ra t nmkhi nng xyanua thp. Khi c c nh, tnh bn ca Cyanide hydratase tng lnnhiu v enzyme t Gloeocercospora sprrghibn vng hn t Stemphylium loti .Cyanidehydratase t nm thch hp x l. cc cht thi cng nghip cha xyanua.

Mt s vi khun Gram-(-) nh Alcaligenes denitrificans cng tit ra cyanidase c ilc bn cao v c kh nng loi xyanua nng rt thp, v d nh < 0.02 mg dm-3CN. Sau ny, khi cng ngh sinh hc pht trin, ngi ta tch c gen cyanidase t

Pseudomonas stutzeri AK61 Pseudomonaspseudoalcaligenes . Hot tnh ca cyanidasekhng b nh hng bi cc ion thng thng c mt trong nc thi (v d nh Fe 2+,Zn2+ v Ni2+), hay bi cc cht hu c nh acatat, formamide, acetamide v acetonitrile.

pH ti u trong khong 7.8-8.3 v mt hot tnh hon ton, khng phc hi khi pH caohn.Ngoi ra con c:

Phng php thy phn/chng ctCN- t thy phn trong nc to thnh dung dch hydrogen cyanide v tip tc bay hi to thnh kh hydrogen cyanide, nhit cao v p lc ln, b bt trong thp hp thuc ra c hoc thng hi vo kh quynu im: Phng php n gin

Nhc im: Yu cu nhit cao, p lc v khng kh ; Sn xut kh hydrogen cyanidemt ln na kh khn c x l .

Phng php thm thu ngcp lc p dng trn mt nc cho i qua mt mng t bo, thm xyanuaYu cu p lc t bn ngoi

u, nhc im ca cc phng php: Phng php oxy ha.

u im: nhanh, khng b nhim bn tr li v CN- b phn hy hon ton.



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Nhc im: iu kin phn ng nghim ngt, cng ngh t tin.

Phng php in ha

u im: cng ngh n gin, x l tt c nc thi xianua bt k nng no.

Nhc: khng hon ton, tiu tn in cc v nng lng nhiu.

Phng php to kt ta

u im: ha cht r, cng ngh n gin

Nhc im: khng hon ton, hiu sut khng cao

Phng php sinh hc u im: Phng php t nhin; C th x l CN- m khng to ra mt dng

thi khc; Khng c x l ha cht thit b , kim sot tn km cn thit ; Chi ph l cnh vi khi lng ln hn cht thi ;Khng c sn phm ph c hi, do thn thin

vi mi trng Nhc im: cng ngh cha c thit l p tt; khng th x l nng

cao Phng php CO2/ khng kh

u im:n gin, r tin, lm vic trong pH rngNhc im: nc c x l t

Cyanide hin ang c x l ch yu da trn cng ngh ha hc, nhng quy trnhx l sinh hc gn y c s dng thnh cng ln quy m hot ng. Vic phttrin v ng dng cng ngh sinh hc phn hy cyanide c gii hn ch yu bi ccyu t vt l. Phng php x l sinh hc thn thin vi mi trng v c th c xem

l ng tin cy v hiu qu kinh t.Trc khi p dng cho bt k qu trnh x no l cn thit bit cc chi tit c tnh ca

cht thi, v hnh thnh v n nh ca cyanide. T c phng php p dng thchhp.3.Phng php xc nh nng xyanua sau khi x l nc thi.

Lng xyanua cn li khng c vt qu 0,01 mg/l ferokalixyanua vferikalixyanua khng vt qu 0,04 mg/l. phn tch xc nh nnng xyanua sau khix l thng dng phng php Colorimetr vi thuc th pirazin ( C 4H4N2 ) cn gi l

phng php Piridin-Pirazin. Phng php ny c chnh xc cao, c kh nng xcnh nng xyanua c vi phn trm miligam xyanua trn mt lt .

- tin hnh phn tch ngi ta phi pha ch mt lot dung dch mu chun :

Cn chnh xc 0,0508 g I2 ha tan trong 100ml CCl4 trong bnh cu nh mc. Ly20ml dung dch ny pha lang bng CCl4 trong bnh cu nh mc n 200ml.

Ly mu 1ml, ln lt pha lang 1, 2, 3,9ml nc nh vy ta c lot mu tngng vi nng xyanua t 0,1 n 1mg/l.



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- Tin hnh phn tch mu: cho vo bnh o dung tch 25ml, 1ml dung dch cn phn tch,sau pha long bng 1ml nc ct.

- Tip theo cho thm 0,1ml dung dch cloramin T 1%. ng cht nt bnh o, lc bnhcn thn. Sau 1pht, thm 4ml thuc th pirazin, ng nt bnh o, lc bnh cn thn.

Dung dch pirazin c chun b nh sau : cn 0,5g pirazin cho vo 100ml nc ct.un dung dch ln 600C, khuy u dung dch, sau khi lm lnh chop nc n th tchyu cu.

- Thm 4ml piridin, y np bnh o, lc u dung dch . em so mu vi dung dch mu trn bng Colorimetr.

KT LUN



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Tinh bt sn hin nay l mt trong nhng ngnh cng nghip rt c quan tm ivi hu ht cc nc ang pht trin. y cng l mt ngnh sn xut s dng nctng i ln v nng cc cht nhim trong nc thi cao.V vy nc thi ra t ccnh my cn c quan tm mt cch c bit v cn c gii php c th m boc mi trng v li ch kinh t.

Vi ti X l nc thi c nhim CN trong qu trnh sn xut tinh btsn,qua qu trnh tm hiu chng ti a ra c nhng phng php x l c hiuqu, m bo mi trng v kinh t lng CN c trong nc thi.

Do kin thc kinh nghim cn hn ch.nn vic tm hiu v xy dng ti khngtrnh khi thiu st rt mong nhn c s ng gp kin ca thy c v cc bn.

TI LIU THAM KHO1. Integrated Treatment of Tapioca Processing Industrial Wastewater Based on

Environmental Bio-Technology - Huynh Ngoc Phuong Mai.2. http://orientbiofuels.com.vn/index.php?option=com_content&view=article&id=67%3Atng-quan-v-cay-sn&catid=48%3Atng-quan-v-cay-sn&Itemid=68&lang=vi3. Destruction of cyanide waste solutions using chlorine dioxide,ozone and titania sol4. X ly nc thi xianua trong cng nghi p m in- Trn Ngc Qunh5. Quy trnh cng ngh tiu hu hoc ti s dng Xyanua

6. Tng lai ng dng Enzyme trong x l ph thi- Tp ch Khoa hc i hc Qucgia H Ni, Khoa hc T nhin v Cng ngh 23 (2007) 75-85.

7. Cyanide Treatment with Hydrogen Peroxide

8. An Overview of Removal Methods of Cyanide from Industrial Wastewater

MC LC

http://orientbiofuels.com.vn/index.php?option=com_content&view=article&id=67:tng-quan-v-cay-sn&catid=48:tng-quan-v-cay-sn&Itemid=68&lang=vihttp://orientbiofuels.com.vn/index.php?option=com_content&view=article&id=67:tng-quan-v-cay-sn&catid=48:tng-quan-v-cay-sn&Itemid=68&lang=vihttp://orientbiofuels.com.vn/index.php?option=com_content&view=article&id=67:tng-quan-v-cay-sn&catid=48:tng-quan-v-cay-sn&Itemid=68&lang=vihttp://orientbiofuels.com.vn/index.php?option=com_content&view=article&id=67:tng-quan-v-cay-sn&catid=48:tng-quan-v-cay-sn&Itemid=68&lang=vihttp://orientbiofuels.com.vn/index.php?option=com_content&view=article&id=67:tng-quan-v-cay-sn&catid=48:tng-quan-v-cay-sn&Itemid=68&lang=vihttp://orientbiofuels.com.vn/index.php?option=com_content&view=article&id=67:tng-quan-v-cay-sn&catid=48:tng-quan-v-cay-sn&Itemid=68&lang=vi


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M u

c vn

Mc tiu v ni dung thc hin

K hiu vit tcCHNG I: TNG QUAN V NGNH SN XUT TINH BT SN

I.Gii thiu chung

1. Cu to c khoai m

2.Phn loi khoai m

3.Tnh hnh sn xut tinh bt sn Vit Nam v th gii:

4.Mt s quy trnh cng ngh sn xut tinh bt.

II.Thnh phn v tc ng ca cc cht ha hc c trong nc thi nh my ch bin

tinh bt sn:1 .Thnh phn cc cht c trong nc thi ca nh my ch bin tinh bt sn2 .Tc ng ca cc cht c trong nc thi

CHNG II : TNG QUAN CC PHNG PHP X L NC THI TRONGNH MY SN XUT TINH BT SN

A.CC PHNG PHP X L

I.PHNG PHP C HC

II. PHNG PHP HA L

III.PHNG PHP HA HC

IV.PHNG PHP SINH HC

1. X l nc thi bng phng php sinh hc trong iu kin t nhin2. X l nc thi bng phng php sinh hc trong iu kin nhn to

B. QUY TRNH X L NC THI NH MY CH BIN TINH BT SN

I.S quy trnh x l nc thi

II. Thuyt minh quy trnh x l nc thiC. CNG NGH THCH HP X L NC THI TINH BT KHOAI MCHNG III: X L XYANUA TRONG NC THI NH MY SN XUTTINH BT SNI.TNG QUAN V XYANUA

1.Tnh cht l hc

2. Tnh cht ho hc



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3. c tnh ca axit xyanhydric v cc xyanua tan

I I . CC P H NG P HP P HT HI N V XC NH HM L NGXYANUA NHIM

1. Phng php nh tnh

2. Phng php nh lng

III.CNG NGH X L XYANUA1.La chn b Acid ho x l nc xianua2. Cc phng php x l xyanua

2.1. phuonwg php oxi ha2.2. Phng php in phn

2.3. Phng php to phc kt ta

2.4.Sc khng kh vo nc thi nhim

2.5.Enzyme x l cht thi xyanua, Cyanide hydratase (cng ngh mi)3.Phng php xc nh nng xyanua sau khi x l nc thi

KT LUN

TI LIU THAM KHOMUC LUC

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